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WARSAW – The failure of rich countries to fulfill a $100 billion promise to help poorer countries adapt to climate change has become a major block at the halfway mark of the United Nations talks now underway in Poland.

The commitment, made by then-Secretary of State Hillary Clinton and other ministers four years ago at the Copenhagen climate talks, has become a "red line" for the developing world, said Meena Raman of the Third World Network.

"These talks will be put in jeopardy if there is no adaptation financing in Warsaw," she said.

Typhoon Haiyan put the issue in the limelight as the UN talks opened, slamming into the Philippines and killing at least 2,350 people. As extreme weather becomes more frequent and severe as a result of increasing emissions, developing countries say they need money now to cope with adaptation efforts as well as so-called "loss and damage."

"This past week we've seen exactly what happens when vulnerable communities are left on their own," said Brandon Wu, a senior policy analyst at ActionAid.

But in some ways the question of how much countries will contribute is premature: The main vehicle for adaptation financing – the "Green Climate Fund" – won't be operational until next year.

"Once that has been finalized, then it will be open for an initial capitalization," said Christiana Figueres, executive secretary for the UN Framework Convention on Climate Change. Talk of specific commitments, she added, "is a question for 2014."

To what extent that disagreement holds up the global climate talks as they head into their second and final week remains to be seen: No one at the Warsaw talks expects a decision limiting emissions from these sessions. The best that can be hoped for, many say, is progress toward a comprehensive global pact at the Paris meeting in 2015.

But for the block of lesser-developed countries at these talks, known as the G77, the issue is paramount, said Lidy Nacpil, a Philippine economist and director of the Asia Pacific Movement on Debt & Development.

"Typhoon Haiyan showed ... that you can't wait anymore," she said. "We hoped this backdrop would galvanize a little more movement."

"Humanitarian aid is not enough," she added. "That's ad-hoc. What we want are permanent solutions."